TRICHINA SPIRALIS 



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and transmigrations of the thirty or more entozoa 

 to which flesh is heir. This chapter of pathology 

 makes up in tragedy what it lacks in romance ; 

 for these animal parasites have killed whole hosts 

 of people. Take, for instance, the trichina spiralis, 

 a minute worm discovered in 1835 encysted in 

 countless numbers in the muscles of the human 

 body ; it was studied by Virchow, Leuckart, 

 and others, by feeding-experiments on animals, 

 and was proved to come from infected half-cooked 

 ham and pork, and to make its way from the 

 alimentary canal all over the body. The name of 

 trichiniasis or trichina-fever was given to the acute 

 illness that came of the sudden dissemination of 

 these myriad parasites into the tissues. Trichi- 

 niasis had killed hundreds of people by a most 

 painful death ; outbreaks of it, in Germany and 

 elsewhere, had swept through villages like cholera 

 or plague : then Leuckart and Virchow traced it 

 to its source, and it was stopped there — Above all 

 things, we must shut off the sources of the in- 

 fection — the butcher's shops were kept under 

 sanitary inspection, people were warned against 

 half-cooked ham and pork, and there was an end 

 of it. 



Or take hydatid disease, which occurs in all 

 parts of the world, and in some countries (Australia, 

 Iceland) is terribly common. The nature of this 

 disease — that it is an animal parasite transmissible 

 between men and dogs — was proved by feeding- 

 experiments on animals. In Iceland, where men 

 and dogs live crowded together in huts, there is 



